For those who want to speedrun this, it's currently unclear what the optimum conversation routing is but it's best you should know the following:

1. Rescuing Clarissa first can save you up to a minute or two, depending on how the conversation post-Ren Rescue goes.
2. Don't bring back Michael. Alex spends some time in the epilogue being confused about his return.
3. Don't investigate the Magnetophone in the Bunker when Jonas asks.
4. Take the easy way out and sacrifice Clarissa when offered in the final showdown.
5. The stations you need to tune into the Portals and or WAL Locks are the same for every playthrough. They are as follows:

Prologue - 88.3 Cave #1 - 105, 98.5, 107 Dorito #1 - 89, 93.7, 91.5 Power Station - 105.5 Dorito #2 - 98.5, 105.5, 99 Fort Milner - 101.8 Classroom - 95.5 Dorito #3 - 106.5, 91.6, 103.6 Dorito Fakeout - 102, 91.6 Adler Gate - 55.6 Adler Door - 117.6 Station Door - 74 Bunker Door - 63 Dorito #4 - 119, 123.5, 126.5 Dorito in the Dorito - 100, 110, (Sacrifice Clarissa)